2019 (2)
By means of Silicon Nano Tweezers (SNTs) the effects on the mechanical properties of λ-phage DNA during interaction with calf thymus nucleosome to form an artificial chromatin analog were measured. At a concentration of 100 nM, a nucleosome solution induced a strong stiffening effect on DNA (1.1 N m− 1). This can be compared to the effects of the histone proteins, H1, H2A, H3 where no changes in the mechanical properties of DNA were observed and the complex of the H3/H4 proteins where a smaller increase in the stiffness is observed (0.2 N m− 1). Para-sulphonato-calix [4] arene, SC4, known for epigenetic activity by interacting specifically with the lysine groups of histone proteins, was studied for its effect on an artificial chromatin. Using a microfluidic SNT device, SC4 was titrated against the artificial chromatin, at a concentration of 1 mM in SC4 a considerable increase in stiffness, 15 N m− 1, was …
Micro-electromechanical system (MEMS) tweezers developed for the trapping and characterization of biomolecules such as DNA are also capable of cell handling, which will enable further application involving single-cell characterization. However, cellular adhesion to Si tweezer surfaces can inhibit the release of cells after capture and analysis. To realize highthroughput cell handling, the surface modification process for probe sidewalls was optimized. The hydrophilicity of sample silicon wafers modified with various chemical coatings was measured to identify the optimal process. The surface modification was then applied to MEMS probes and the feasibility of cell capture/release was evaluated.
2018 (2)
The couple Calix [4] arene-1, 3-O-diphosphorous acid (C4diP) and zinc ions (Zn 2+) acts as a synergistic DNA binder. Silicon NanoTweezer (SNT) measurements show an increase in the mechanical stiffness of DNA bundles by a factor of> 150, at Zn 2+ to C4diP ratios above 8, as compared to Zinc alone whereas C4diP alone decreases the stiffness of DNA. Electroanalytical measurements using 3D printed devices demonstrate a progression of events in the assembly of C4diP on DNA promoted by zinc ions. A mechanism at the molecular level can be deduced in which C4diP initially coordinates to DNA by phosphate-phosphate hydrogen bonds or in the presence of Zn 2+ by Zn 2+ bridging coordination of the phosphate groups. Then, at high ratios of Zn 2+ to C4diP, interdigitated dimerization of C4diP is followed by cross coordination of DNA strands through Zn 2+/C4diP inter-strand …
Micro-Electro-Mechanical-System (MEMS) devices associated to Transmission Electron Microscopes (TEM) have demonstrated their high potential for atomic resolution imaging of specimen while applying stress for mechanical testing. This paper introduces a novel actuation principle for the MEMS device in TEM relying on the internal magnetic field of the TEM and current flow through the device. The actuation principle is experimentally demonstrated in TEM and entirely modeled in the case of a silicon beam. The model is validated through static and dynamic experimental studies. The thermal side-effect of current flow is taken into account. The major advantages of the proposed magnetic actuation principle are the bidirectional control of the displacement of the device, the intrinsic linear displacement of the device with applied current and the potential milliNewton (mN) range force generation.